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Diffuse noxious inhibitory control

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Diffuse Noxious Inhibitory Controls (DNIC) refers to an endogenous pain modulatory pathway which has often been described as "pain inhibits pain". [1] It occurs when response from a painful stimulus is inhibited by another, often spatially distant, noxious stimulus.

Mechanism

Nociceptive noxious stimulus is carried by C and Aδ fibers to the dorsal horn of spinal cord. Dorsal horn thus receives both the noxious and the innocuous stimuli. DNIC refers to the mechanism by which dorsal horn convergent neurons carrying nociceptive response for one location of the body may be inhibited by peripheral noxious stimuli (such as heat, high pressure or electric stimulation) from another remote location in the body. [1] The inhibition is thought to be supra-spinal in origin effecting the wide dynamic range and nociceptive neurons in the dorsal horn (Le Bars 2002).

Studies investigating gender differences in DNIC have shown mixed results with the effect dependent upon experimental methodology and measurement method. [2]

Measurement Method

Increased pressure pain threshold (PPT) and pain tolerance (PTol) parameters are widely used as a measure of DNIC. Equipments such as metal pressure algometer with a rubber top is used to apply pressure to a person's finger or toe. The pressure at which the first sensation of pain is felt is recorded as PPT. The pressure is increased further and noted when the person complains of the intolerable pain. This higher value is recorded as PTol. A second noxious stimulus (such as ice water or warm water) is then applied to a different part of the body and PPT/PTol measured thereafter. DNIC response is defined as an increase in the value of PPT during the second noxious stimulation.

Clinical Use

DNIC model is used frequently to quantify the central pain sensitization in chronic pain patients. DNIC inefficiency (or lower DNIC) has been implicated as a risk factor for development of chronic pain and pain syndromes. On the other hand, greater DNIC response is related to less pain, better physical functioning, and better self-rated health. [3]

Chronic pain disorders such as temporomandibular disorder (Kashima 1999) and fibromyalgia (Lautenbacher 1997) have been associated with DNIC inefficiency.

DNIC forms the basis for the use of counterirritant to reduce pain.

See also

References

  1. ^ a b D. Le Bars, A.H. Dickenson and J.M. Besson (1979). "Diffuse noxious inhibitory controls (DNIC). Effects on dorsal horn convergent neurones in the rat". Pain. 6: 283–304.
  2. ^ Popescu A, LeResche L, Truelove EL, Drangsholt MT (2010). "Gender differences in pain modulation by diffuse noxious inhibitory controls: a systematic review". Pain. 150(2): 309–314.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ^ Edwards RR, Ness TJ, Weigent DA, Fillingim RB (2003). "Individual differences in diffuse noxious inhibitory controls (DNIC): association with clinical variables". Pain. 106(3): 427–37.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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